For supernova shocks propagating through the partially ionized interstellar
medium,
we discuss the turbulent dynamo as a mechanism for amplifying the preshock magnetic fields.
Given the parameters adopted here, Eq. (REF ) provides an estimate for the maximum energy of CRs
that the dynamo-amplified magnetic fields can confine.
The detailed modeling of shock acceleration of CRs that involves the dynamo-amplified magnetic fields
and the dependence of the maximum CR energy on the local interstellar environment
require further studies.
We also note that the recent observations of SNRs suggest that the maximum energy of accelerated CRs is below 1 PeV
(e.g., [1]}, [2]}).
In these observed SNRs,
the magnetic field amplification may not be very efficient.
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